High performance engines used in modern vehicles tend to operate at a higher temperature than internal combustion engines of several years ago. As a result the temperature of the exhaust manifold and other component parts rises to where the components may be "red hot". The problem is that operating apparatus within the engine compartment having rubber, plastic or other non-metal, non-steel components, may be subjected to radiant heat from the hot body and thereby prematurely deteriorate the desired operating parameters of the operating apparatus. Examples of operating apparatus which fall into this category are alternators, starter motors and turbo chargers.
There is a need to provide a heat shield or heat barrier between the hot body and the operating apparatus which is structured in a way to minimize heat build up in the operating apparatus as a result of radiant heat from the hot body.
A patent to Engquist et al., U.S. Pat. No. 4,612,767, discloses a heat shield mounted to an exhaust system designed to reflect heat back toward the exhaust system. The shield includes a plurality of spaced apart layers structured to facilitate a convective air flow to cool the spaced apart shield elements. The engine reaches steady state operating temperatures and over time the layered heat shield also reaches steady state operating temperatures which are obviously going to be below the operating temperature of the exhaust system which it encompasses. The degree of heat shielding by the apparatus illustrated in the patent is controlled in part by the temperature of the air flowing in the convection passages.
A patent to Schmidt, U.S. Pat. No. 4,878,467, discloses a protective heat cover for traction drives. The invention disclosed is of a closed body surrounding a traction drive which is cooled by air pumped from an outside system through the closed body. The intent is to cool by air pumped into the system rather than shielding outside operating components from the heat of radiation generated by the traction drive. Nevertheless, the structure illustrated inherently serves as a heat shield to operating components which might be in the vicinity of the hot traction drive. The emphasis in this patent is on heat transfer by induced air flow rather than shielding other components from radiation.
A patent to Deuring, U.S. Pat. No. 4,928,980, discloses a cover for motor vehicle crankcases and gear boxes. The cover inherently reduces radiation to other components not illustrated.
The most pertinent prior art appears to be a patent to Whitehurst, U.S. Pat. No. 5,233,953, which discloses a spring steel heat shield for snapping onto the periphery of a starter motor solenoid. The structure minimizes radiant heat directed toward the solenoid from an exhaust system. The problem is that the heat shield is spring steel itself and over a period of time at steady state operation the shield continues to rise in temperature and to a certain extent will defeat the intended purpose although it is certainly better than nothing. The disclosed shield may well be effective in extending the life of the components of the starter motor which may be adversely affected by elevated temperatures.
There is a need in the industry for a heat shield to surround or partially encompass operating apparatus within a vehicle engine compartment which provides a rather substantial heat gradient across the shield between a high temperature heat source and the surface of the operating apparatus to be protected.